did you read this part of the DIY? is this what is giving you problems?
By moving and twisting things to better line up, I got the muffler into position, but had a brake line holder clearance problem as shown in this pic. A quick whack with a hammer on a wooden block "adjusted" the brake line holder enough to move it out of the way for the muffler. AP's instructions warn you that brake line clearance might be a problem and shows you how well they know their product.
